1. Field of the Invention
The present invention relates generally to extending the life of back-up batteries used in an outdoor equipment cabinet and, more particularly, to a novel battery cooling system which maintains the temperature of back-up batteries at an ideal level despite temperature extremes imposed by ambient conditions.
2. Description of the Related Art
Many forms of electronic equipment, of necessity, must be located in an outdoor environment. Such equipment in typical form may be telecommunications and cable television equipment including active electronic and optical systems and passive cross-connect and splicing fields. It is essential that such equipment be protected from a wide range of ambient temperatures and inclement climatic conditions such as rain, snow, sleet, high winds and sand storms as well as other in situ environmental issues like seismic vibration, etc. To this end, cabinet enclosures have been developed to house such electronic equipment in a highly weather tight manner.
The type of electronic equipment that is typically housed in an outdoor cabinet, particularly in active systems, is known to generate considerable amounts of heat in operation. Further, in many environments the ambient air can become very warm and heat up the air internal to the cabinet. Many active systems enclosed in outdoor equipment cabinets employ battery back-up means to ensure reliable performance. Often the batteries are of a lead-acid construction which is known to be adversely affected by temperature extremes in terms of battery life. In fact, a standard lead-acid battery performs optimally at a temperature of about 25xc2x0 C., as opposed to more elevated temperatures which can reach as high as 65xc2x0 C. in some outdoor environments. At 25xc2x0 C. battery life is about 10 years. However, for every 10xc2x0 C. increase battery life is cut in half. Temperature fluctuations also are detrimental to battery life.
Systems are known for cooling batteries for outdoor equipment cabinets exposed to relatively high ambient temperatures. For example, Han et al., U.S. Pat. No. 5,934,079, teach a cabinet wherein back-up batteries are disposed underneath a heat sink through which air circulates at a regulated temperature utilizing forced convection heat transfer. Other known convection systems includes the CHAMPION THERMOSAFE cooling system, a thermoelectric device having a very low coefficient of performance. A Zome Work COOL CELL cooling system uses a water thermosyphon. Another company buries the batteries underground but this also has many drawbacks including the need for additional equipment.
Another drawback to existing systems is that they may be stand alone units instead of being integrated with the equipment cabinet.
It is important to develop a system which does not expose batteries to high temperatures or substantial temperature variations if long life for the battery is an objective. For commercial purposes, such a system must be reliable, efficient and reasonably priced.
Accordingly, it is an object of the present invention to provide a battery cooling system for back-up batteries used for outdoor equipment cabinets wherein the batteries are consistently maintained at a predetermined constant temperature (or within a very small temperature range), and preferably a temperature on the order of 25xc2x0 C. Another advantage of the present invention is to provide such a battery cooling system which is incorporated in an outdoor equipment cabinet of known design without major redesign of the cabinet. Still further, an aim of the present invention is to provide such a system which is readily manufacturable and cost-effective to produce. Another object of the present invention is to extend battery life. Yet another advantage of the present invention is that it is highly reliable.
The present invention improves over the prior art by providing an apparatus for extending the useful life of a lead-acid type battery by applying conductive cooling directly to the bottom surface of the battery to maintain a constant temperature of about 25xc2x0 C. regardless of the ambient temperature surrounding the battery.
A more complete understanding of the present invention and other objects, aspects, aims and advantages thereof will be gained from a consideration of the following description of the preferred embodiments read in conjunction with the accompanying drawings provided herein.